Hub, Switch, Bridge & Router

Hub

A network hub or repeater hub is a device for connecting multiple twisted pair or fiber optic Ethernet devices together and thus making them act as a single network segment. Hubs work at the physical layer (layer 1) of the OSI model. The device is thus a form of multiport repeater. Repeater hubs also participate in collision detection, forwarding a jam signal to all ports if it detects a collision.




Switch

Switches are really just multiple port bridges with more intelligence. A switch is to make a LAN work better, to optimize its performance and providing more bandwidth for the LAN’s users. Switches use in a network are to reduce collisions within broadcast domains and to increase the number of collision domains in the network. Doing this provides more bandwidth for users. Switches only “switch” frames from one port to another within the switched network.




Bridge

Bridges and switches basically do the same thing such break up collision domains on a LAN. Now, we cannot buy a physical bridge these days, only LAN switches, but they use bridging technologies. A bridge works at the data-link level of a network.

Router

A router is a networking device whose software and hardware are usually tailored to the tasks of routing and forwarding information. For example, on the Internet, information is directed to various paths by routers. Routers connect two or more logical subnets, which do not necessarily map one-to-one to the physical interfaces of the router. The term "layer 3 switches" often is used interchangeably with router. Router will not only break up broadcast domains for every LAN interface, it will break up collision domains as well.

Difference between hub, switch, bridge, router

Hubs create one collision domain and one broadcast domain. Bridges break up collision domains but create one large broadcast domain. They use hardware addresses to filter the network. Switches are really just multiple port bridges with more intelligence. They break up collision domains but create one large broadcast domain by default. Switches use hardware addresses to filter the network. Routers break up broadcast domains (and collision domains) and use logical addressing to filter the network.